The present invention relates to a method for manufacturing an insulating pack for an insulation part in particular for a heat shield, the insulating pack having at least two stacked metallic sheets; to an insulating pack manufactured therewith in particular a heat shield, with several stacked, metallic sheets; as well as to a separating tool for carrying out the method, the separating tool having two separating flanks, the separating flanks having different angles to a contact surface.
In the motor vehicle industry, as well as in other technical fields, there exists a requirement for thin thermic insulation parts which may be adapted to their application purpose in a simple manner. It is therefore desirable to be able to economically manufacture such insulating parts, in particular thin heat shields, which may be brought into the desired shape in a simple manner. Known insulation parts are constructed of a stack of several aluminium foils or aluminium sheet metals. Such insulation parts find an increasing application with heat shields for vehicles.
Such a heat shield is for example disclosed in U.S. Pat. No. 5,011,743 and its corresponding application WO 91/10560. These documents disclose a foil package which comprises heat-conducting zones, so called heat sinks, and heat-insulating zones. In particular these foils comprise embossings or naps which result in the stacked foils being distanced from one another. The individual foils may be connected to one another in a hermetically sealed manner, by which means the enclosure of a gas e.g. xenon is made possible. In a further embodiment of this invention the individual foils are perforated for improving the acoustic effectiveness. The edge regions of this foil package are in practice pressed together with a considerable pressure force and are cut in separate method steps, and are subsequently crimped, heat sealed or mechanically connected. With these known foil packages, and due to mechanical strain which is, for example, exerted during transport or during operation, the foils may separate again in the connection region.
The above described insulating pack or heat shield has a number of disadvantages. One disadvantage which becomes obvious to the man skilled in the art lies in the fact that heat flows through the heat sink regions onto the other side of the insulation part and on account of the relatively wide border regions, the proportion of the effective insulation surface on the whole heat shield is undesireably reduced. Furthermore, the conventional manufacture of such heat shields has shown to be complicated with respect to tooling. On account of the sharp points occurring when using stretch sheet metal and the high risk of injury to personnel related to this, such stretch sheet metal is not applied.
It is therefore the aim of the present invention to provide an inexpensive method, i.e. simple with respect to tooling, for manufacturing an insulating pack or pad for an insulation part or a heat shield, which permits in as few operating steps as possible a processing-friendly and safe heat shield to be manufactured from a stack of metallic sheets, wherein the individual sheets of this stack in their edge regions are firmly connected to one another, without at the same time heat sinks being formed.
In the following metallic sheets are to be understood in general being extended metal parts. These extended metal parts may have differing thicknesses, may be perforated or have a particular structure. In particular these are to be understood as perforated (having holes or being fissured) or unperforated foils, thin metal sheets or metal sheeting, foils in the form of stretch metal grids, stretch foils, metal knittings, metal weavings, metal tissue or similar surfaced structures. These sheets may also be coated or comprise honeycomb-like deformation patterns (honeycomb-sheet-metal) or may be shaped in a different manner, in particular may be napped.
This aim is achieved according to the invention by cold welding or metallurgically connecting, with the aid of a separating knife, a predetermined region of stacked metallic sheets along a contour of the region whilst forming a continuous welding seam and simultaneously separating the stacked metallic sheets from a residual region, and in particular by a method for manufacturing an insulating pack with a stack of several metallic sheets, which may be embossed and/or perforated, and with this method the individual sheets of the stack are continuously cold-welded in their peripheral region and at the same time are separated from the residual material. Cold-welding in the following is to be understood as a metallurgical connection or bonding which is achieved by means of a plastic deformation of two or more neighbouring sheets, and with this deformation the metallic material of neighbouring sheets integrally connects. With aluminium such a connection may be achieved when the material is compressed for example by approx. 75%.
With the method according to the invention at least two metal sheets are stacked, wherein individual sheets may be embossed. According to the invention, the stack produced in such a manner is cold-welded along a predetermined contour and at the same time is separated from the cutting waste. This is preferably achieved with a mould press equipped with a suitable separating tool. It is to be understood that this cold-welding of the stack periphery and the separation of the individual sheets of the stack may also be accomplished with other suitable separating tools.
Furthermore with this cold-welding method an insulating pack consisting of a multitude of differing (for example napped, holed, or grid-like) sheets, foils or sheet metals may be manufactured. With the application of stretch metal sheeting, edges may be produced which do not have any sharp points. The method according to the invention furthermore permits insulating packs to be deformed in a suitable manner. In particular, the application of stretch-metal-like sheets, in contrast to s perforated sheets, has proven to be particularly advantageous, since such stretch metal sheets are lighter, more easily deformable and tear less easily. Furthermore the acoustic effectiveness of these stretch-metal-like sheets may be controlled or adjusted in a simple manner by the formation of differently large openings.
It is further the aim of the present invention to provide an acoustically effective insulating pack, in particular a heat shield with a stack of metallic sheets, which overcomes the above cited deficiencies, wherein the individual sheets of this stack in their edge regions are firmly connected to one another, without at the same time heat sink regions being produced. Furthermore an insulating pack is to be provided which may be deformed in a simple manner without at the same time becoming damaged or separating during transportation or use.
According to the invention this aim is achieved by an insulating pack or pad with several stacked, metallic sheets, having a continuous cold-weld seam along its contour, and in particular by an insulating pack in which the individual sheets of the stack are cold-welded to one another along their common edges. In one preferred embodiment of this insulating pack the cold-weld seam is approx. 0.3 mm wide. In another particular embodiment the insulating pack comprises at least one stretch sheet metal. In another particular embodiment the insulating pack is provided with at least one fold line in order to permit a strong deformation of the whole insulation package in a simple manner; and in yet another particular embodiment at least one of the metallic sheets of the insulating pack is napped and/or perforated.
In a preferred embodiment of the present invention the insulating pack or heat shield comprises a plurality of aluminium foils which are cold-welded to each other along their respective edges. With these cold-welded foils a peripheral connection is produced which is substantially more stable than the embossing or adhesing methods which are disclosed in the state of the art, for example in U.S. Pat. No. 5,011,743. The inventive insulating pack is welded only along its edge or peripheral regions, which ensures good heat insulating properties over the entire inner region.
In a preferred embodiment the insulating pack comprises a multitude of stacked metal foils, as well as a carrier sheet metal and a cover foil or a cover sheet metal. With this embodiment the carrier sheet metal consists of a stretch metal or a perforated sheet metal. In a particular embodiment the invention comprises a foil stack, with which the individual foils are perforated and are fastened on a perforated carrier sheet metal. According to the invention with all these embodiments at least the foils of the foil stack are cold-welded to one another. It is however to be understood that the foils of the foil stack may also be cold-welded directly to the carrier sheet metal and/or to the cover foil.
It is an additional aim of the present invention to provide suitable means for carrying out the method according to the invention.
According to the present invention this additional aim is achieved by use of a separating knife, and in particular by use of a separating knife, whose separating flanks preferably inclined to a differing degree to the separating plane. In a particularly preferred embodiment a first separating flank is at an acute angle of approx. 60xc2x0 to the contact surface and a second separating flank is at a less acute angle of approx. 25xc2x0 to the contact surface. A further embodiment of this separating knife is formed as a round knife.
By applying a separating tool it is possible to produce such a cold-welding along the edges of the stack of metallic sheets. In this way the individual sheets are simultaneously connected to one another and brought into a special contour.
A particularly advantageous formation of the separating tool comprises a separating knife which has an acute angle of preferably 60xc2x0 between a first separating flank and the cold-welding plane and which separating knife has an acute angle of preferably 25xc2x0 between a second separating flank and the cold-welding plane in such a manner that between the two separating flanks of the separating knife there is formed an obtuse angle of, for example, 95xc2x0.
The inventive application or use of cold-welding has proven to be considerably advantageous with respect to known methods for connecting the individual sheets of a stack, inasmuch as such cold welding can be carried out considerably more simply and quickly, as well as more economically and safely. When this cold-welding method is combined with a separating step, the number of method steps for manufacturing such insulating packs can be considerably reduced as compared to conventional methods (in particular as compared to complicated crimping methods).
The insulating pack according to the invention does not have any disadvantageous heat sinks but rather comprises an extremely narrow region in which the individual sheets have an integral connection to another and thus in a reliable and long lasting manner. Furthermore, the insulating packs manufactured according to the invention, and even when using stretch-metal-like sheets, do not have any sharp points and may be folded into any desired shape at their fold lines, without at the same time tearing, breaking or coming apart at their edge regions. Furthermore the geometric course of the cold-welded connection may be shaped in any manner, i.e. as a serpentine line or complementarily to the geometric course of the edge region of a neighbouring insulating pack, and in particular a heat shield which is to be manufactured from the same sheets. In particular, it is thus possible to minimise the cutting waste during manufacture of these insulating packs.